Clearance unloader for compressors



Aug. 9, 1932. R. c. M ALLI STER 1,870,956

' CLEARANCE UNLOADER FOR COMPRESSOBS Filed Ju1 .14. 19:51

Patented Aug. 9, 1932 UNITED STATES RAYMOND c. MCALLISTER, 0F PAINTED rosr, NEW' YORK, AssIeNoRf'ro INGERSOLL RAND COMPANY, OF JERSEY crrY, NEW JERSEY, AfooEronA'rIo or NEW J S Y" CLEARANCE UNLOADER FQIt comrsnssons p Application filed July 14,

This invention relates to compressors, but more particularly to compressor unloaders using clearance chambers.

The objects of the invention are to enable a plurality of unloading steps to be obtained by means of clearance chambers and clearance valves. By operating the clearance valves in proper predetermined order the desired number of steps of unloading is obtained.

Other objects will be in part obvious and in part pointed out hereinafter.

Referring more particularly to the drawing the cylinder 10 having the piston 12 receives air or gas from the intake 14 and discharges it from the discharge outlet 16 to a receiver 17. The compressor is provided with the usual inlet and discharge Valves 18 and 20 which may be plate valves.

Clearance chambers, 22, 24 and 26 of equal volumes, having clearance valves 28, 30, 32 and 34, are provided for the cylinder 10 and each clearance valve has a valve opening mechanism comprising pistons 36 operating in cylinders 38. Springs 40 normally keep the valves closed and they are opened by fluid pressure supplied through pipes 42, 44,- 46 and 48, (which lead from the ports 41, 43, and 47 respectively).

A regulator automatically controls the clearance valves and the regulator is constructed as follows:

A cylinder 50 is provided with a piston 52 and two cylinder heads 51 and 53, one end of the piston 52 is subject to receiver pressure through the pipe 54. An adjustable spring 56 returns the piston when pressure is released from the opposite end. A pin 58 in. a slot 60 in the piston prevents rotation of the piston relative to the cylinder. A vent 62 in the wall of the cylinder permits the escape of pressure fluid from the end of the cylinder in which the vent is formed. Adjustment of the tension in the spring is accomplished by means of an adjusting screw 64 threaded into the cylinder head 51. The piston 52 is cut away at 66 and 68 so that as the piston moves to the left as viewed in the drawing the ports 47,45, 43 and 41 are uncovered step by step. The cut-away portion 66 of the 1931,; Serial Nassofias.

piston 52 determines, that only the ports in connection with cutaway. portion 68shall be exposed to greater pressure than. atmospheric asthe other pipes willdischarge into the cylinder and through the vent 62."

The. operation of the device is as follows: Assuming-for example that the pressure inthecompressor receiver is to be maintained at constant pressure, the'spring 56 is adjusted accordingly. It receiver pressure tends to rise above the predetermined amount the piston 52 ismoved to the left by-receiver pressure entering the cylinder '50 through the pipe 54. .Port '47 is uncovered and pressure fluid enters cylinder 38' through pipe 48*causing piston 36 to niove jupwardopening valve 28. The capacity of the'clearance pocket '22is such that the opening of valve 28 causes the compressor to operate at three quarters load. If receiver pressure still tends to increase valves 32, 34 and 30 are opened in turn by the movement of piston 52 thus causing the compressor to operate at one-half load, one quarter load and'no load respectively. (At no load the gas is by-passed from one end of the cylinder 10 to the other through chamber 22.)

At higher receiver pressures, with valve 28 open, the compressor operates at threequarters load, with valves 28 and 32 open the compressor operates at one-half load, with valves 28, 32 and 34 open the compressor operates at one quarter load, with valves 28, 30, 32 and 34 open the compressor operates at no load, the gas-being by-passed from one end of the cylinder 10 to the other through chamber 22. Thus the objects hereinbefore mentioned are accomplished.

I claim:

1. In a compressor unloader the combination of a cylinder and piston, inlet and discharge valves, a receiver, a plurality of clear- .ance pockets of equal volumes, a plurality of clearance valves controlling communication between the cylinder and the clearance pockets, one of the clearance pockets being provided with two clearance valves permitactuating the clearance valves to unload and load the compressor in steps.

2. In a compressor unloader the combination of a cylinder and a piston, inlet and discharge valves, a receiver, three clearance pockets of equal Volumes, four clearance valves controlling communication between the cylinder and the clearance pockets, the

clearance pockets and clearance valves being so arranged that each end'of the cylinder may 7 communicate with two clearance pockets and fluid actuated means responsive to receiver pressure for actuating the clearance valves to unload and load the compressor in steps.

3. In a compressor unloader the combination of a cylinder and piston, inlet and discharge valves, a receiver,-a plurality of clearance pockets of equal volumes, a plurality of clearance valves controlling communication between the cylinder and the clearance pockets, one of the clearanoepockets being provided with two clearance valves permitting communication between that pocket and both ends ofthe cylinder allowing fluid to be by-passed from'one end of the cylinder to the other when the compressor is operating at no load, and fluid actuated means respon sive to receiver pressure for actuating the clearance valves to unload and load the com pressor in steps. e

In testimony whereof I have signed this specification. v

RAYMOND G. MCALLISTER. 

